Despite sustained interest in the optical, electronic, and theranostic applications of functionalized nanomaterials, their controlled and reproducible synthesis, particularly above the milligram scale, remains a challenge. Most functionalized nanoparticles (NPs) are still synthesized using discovery-phase synthetic strategies (low-yield, high-waste, low-throughput) and purification approaches which are inefficient and generally not amenable to scale up. As nanotechnology enters a more application-oriented phase, however, kilogram-scale quantities of monodisperse NPs may be desperately needed to verify NP performance in biomedical applications, develop prototype devices, and adequately assess their potential toxicity.
For instance, it has been calculated that, in order to supply every person on earth with a 10 nm thick, 2.25 cm2 monolayer of gold nanoparticles (e.g., as a standardized dose for theranostic anti-cancer treatments), gold nanoparticles would have to be reliably produced on the 100 kg scale. Currently, even though gold nanoparticle (AuNP) synthesis has been extensively researched for decades, few synthesis methods produce AuNPs on greater than a 50 mg scale. A typical approach, the standard seeded-growth synthesis of gold nanorods (AuNRs), produces less than 10 mg of AuNRs per batch.
Though it may seem conceptually simple, the scaling up of gold nanoparticle synthesis is a significant challenge; increasing the concentration of the reagents in the growth solution, or even the volume of the reaction, can significantly alter the rates reagent diffusion and thermal transport, effectively resulting in a loss of control over product properties. In order to meet the demand for nanoparticles for testing and prototype development, it would be advantageous to develop new strategies and infrastructure for nanomaterial synthesis.